On-site cleaning gas generation for process chamber cleaning

ABSTRACT

Provided herein is a method for cleaning a process chamber for semiconductor and/or flat panel display manufacturing. This method comprises the steps of converting a non-cleaning feed gas to a cleaning gas in a remote location and then delivering the cleaning gas to the process chamber for cleaning. Such method may further comprise the step of activating the cleaning gas outside the chamber before the delivery of the gas to the chamber. Also provided is a method of eliminating non-cleaning feed gas from the cleaning gas by cryo condensation.

This application is a continuation of U.S. patent application Ser. No.09/741,529, filed Dec. 19, 2000, now issued as U.S. Pat. No. 6,843,258,which is herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the field of semiconductormanufacturing. More specifically, the present invention relates to amethod of on-site cleaning gas, e.g., F₂, generation for semiconductorand/or flat panel display process chamber cleaning, and a method ofeliminating HF from F₂ generator by, for example, cryo condensation.

2. Description of the Related Art

One of the primary steps in the fabrication of modern semiconductordevices is the formation of a layer or film on a substrate. As is wellknown in this art, such a layer can be deposited by chemical vapordeposition (CVD). In a conventional plasma-enhanced CVD (PECVD)processes, a controlled plasma is formed using radiofrequency (RF)energy or microwave energy to decompose and/or energize reactive speciesin reactant gases to produce the desired film.

One problem that arises during such CVD processes is that unwanteddeposition occurs on some or all of the processing chamber's interiorsurfaces, leading to potentially high maintenance costs. With CVD of adesired film onto a substrate, the deposition of undesired residues canoccur on any surface, because the reactive gases can diffuse to mostparts of the processing chamber, even between cracks and around corners.During subsequent substrate depositions, these residues can accelerateuntil a continuous film is grown on the undesired parts. Over time,failure to clean the residue from the CVD apparatus often degradesprocess yield.

When excess deposition starts to interfere with the CVD system'sperformance, various parts of the chamber can be replaced to removeunwanted accumulations thereon. However, the replacement wouldpotentially increase the maintenance cost. Moreover, such maintenanceadversely affects throughput of the CVD system. Therefore, cleaning ofthe processing chamber is regularly performed to remove such unwantedresidues from the chamber walls, heater, and other process kit parts.

Commonly performed between deposition steps for every substrate (orevery n substrates), in situ cleaning procedures using one or morecleaning (i.e., etchant) gases are performed to remove the unwantedresidual material accumulated during the deposition process. Commoncleaning techniques known to those having ordinary skill in this artinclude thermal, RF plasma, and microwave plasma techniques.

A radiofrequency plasma cleaning process could use nitrogen trifluoride(NF₃), for example, because such a technique is capable of imparting thehigh energies required to dissociate a more stable compound. First, NF₃is flowed into the processing chamber being cleaned. Radiofrequencyenergy is then applied (e.g., via the substrate processing system'scapacitively coupled electrodes), thus generating the fluorine radicals(F*) which remove the unwanted residues from the processing chamber'scomponents. A frequency of 13.56 megahertz (MHz) is commonly used toexcite the plasma.

However, the radiofrequency plasma process using NF₃ could be costly, asNF₃ is very expensive. Other gases such as SF₆ and C₂F₆ are cheaper, butusually cause significant environmental pollution. Therefore, the priorart is deficient in the lack of effective and economic means of cleaninga semiconductor and/or flat panel display process chamber with minimalenvironmental pollution. Specifically, the prior art is deficient in thelack of effective means of cleaning a process chamber by generating thecleaning gas, such as, F₂ on site and further delivering the cleaninggas to the chamber so that the HF is eliminated from the F₂ generator bycryo condensation. The present invention fulfills these long-standingneeds and desires in the art.

SUMMARY OF THE INVENTION

Provided herein in one embodiment of the present invention is a methodfor cleaning a process chamber for semiconductor and/or flat paneldisplay manufacturing. This method comprises the steps of converting anon-cleaning feed gas to a cleaning gas in a remote location and thendelivering the cleaning gas to the process chamber for cleaning. Thismethod may further comprise the step of activating the cleaning gasoutside the chamber before the delivery of the gas to the chamber.

Also provided herein in another embodiment of the present invention isan alternative method for cleaning a process chamber for semiconductorand/or flat panel display manufacturing. This method comprises the stepsof converting a feed gas to a cleaning gas in a remote location, whereinthe resulting gas is a mixture of the feed and cleaning gas;transferring the resulting gas mixture to a cold trap, wherein the feedgas is turned into a liquid form, and the cleaning gas remains in agaseous form; and delivering the cleaning gas to the process chamber forcleaning. This method may further comprise the steps of pumping thecleaning gas into a storage unit and/or activating the cleaning gasoutside the chamber before the delivery of the cleaning gas to thechamber.

Other and further aspects, features, and advantages of the presentinvention will be apparent from the following description of theembodiments of the invention given for the purpose of disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the matter in which the above-recited features, advantages andobjects of the invention, as well as others which will become clear, areattained and can be understood in detail, more particular descriptionsof the invention briefly summarized above may be had by reference tocertain embodiments thereof which are illustrated in the appendeddrawings. These drawings form a part of the specification. It is to benoted, however, that the appended drawings illustrate embodiments of theinvention and therefore are not to be considered limiting in theirscope.

FIG. 1 is a schematic drawing in accordance with one embodiment of thepresent invention. The feed gas (e.g., HF) is eliminated from thecleaning gas (e.g., F₂) generator by cryo condensation, and then thepurified cleaning gas is delivered into a storage unit before itsarrival to the PECVD process chamber.

FIG. 2 is a schematic drawing in accordance with another embodiment ofthe present invention. The feed gas is eliminated from the cleaning gasgenerator by cryo condensation, and the purified cleaning gas isdelivered into a storage unit. The cleaning gas is then activated beforeits arrival to the PECVD process chamber.

DETAILED DESCRIPTION

Provided herein in one embodiment of the present invention is a methodof on-site cleaning gas generation for a semiconductor and/or flat paneldisplay process chamber cleaning. A cheap feed stock gas, such as HF maybe used instead of the expensive NF₃. HF itself does not clean thechamber. However, when HF is electrolyzed, the resulting F₂ may be usedas a cleaning gas.

To clean the process chamber, the feed gas, e.g. hydrogen fluoride, isused as a precursor to form a cleaning gas (F₂) in a remote location(i.e., pump garage area). That is, the F₂ cleaning gas is generatedon-site. Then F₂ is delivered to the chamber for chamber cleaning.Optionally, the cleaning gas F₂ can be activated outside the chamber toincrease the cleaning efficiency via a remote plasma source (RPS).During the activation, F₂ is chemically turned into 2F, i.e. twoequivalents of atomic fluorine (F), in the plasma excitationenvironment.

A typical method of generating F₂ from HF is electrolysis (HF→F₂+H₂).After electrolysis, the F₂ and any residual HF in gaseous form aretransferred from the generator to a cold trap cylinder, wherein the F₂and HF are separated (FIGS. 1 and 2). Specifically, the cold trap turnsHF into a liquid state, while F₂ is pumped into the 100-liter storagecylinder, and further supplied to the process chamber. The byproduct ofthe electrolysis H₂ is sent to an exhaust system.

The present method reduces the cost of chamber cleaning and eliminatesthe use of global warming gas. Due to safety concerns, F₂ is generatedon-demand to minimize the need for storage. However, a mini-storagedevice can be used. Additionally, the method of eliminating HF from thegenerated cleaning gas by cryo condensation has several advantages overthe state-of-art methods which uses sodium fluoride trap. For example,the changing cold trap does not require any maintenance; and secondly,sodium contamination is eliminated from the gas line.

As described above, provided herein is a method for cleaning a processchamber for semiconductor and/or flat panel display manufacturing. Thismethod comprises the steps of converting a non-cleaning feed gas to acleaning gas in a remote location and then delivering the cleaning gasto the process chamber for cleaning. Such a method may further comprisethe step of activating the cleaning gas outside the chamber before thedelivery of the gas to the chamber. Specifically, the activation may beperformed through a remote plasma source, a heat source, or anelectrical source. Representative examples of a remote plasma sourceinclude a microwave energy source or a radiofrequency energy source.

In this method, an example of the non-cleaning feed gas is HF, and thegenerated cleaning gas is F₂. In one aspect, the conversion is donethrough electrolysis.

Also provided herein in another embodiment of the present invention isan alternative method for cleaning a process chamber for semiconductorand/or flat panel display manufacturing. This method comprises the stepsof converting a feed gas to a cleaning gas in a remote location, whereinthe resulting gas is a mixture of the feed and cleaning gas;transferring the resulting gas mixture to a cold trap, wherein the feedgas is turned into a liquid form, and the cleaning gas remains in agaseous form; and delivering the cleaning gas to the process chamber forcleaning. This method may further comprise the steps of pumping thecleaning gas into a storage unit and/or activating the cleaning gasoutside the chamber before the delivery of the gas to the chamber.Specifically, the activation may be performed through a remote plasmasource, a heat source, or an electrical source. Representative examplesof remote plasma sources familiar to those having ordinary skill in thisart include a microwave energy source or a radiofrequency energy source.

Further in this method, an example of the non-cleaning feed gas is HF,and the generated cleaning gas is F₂. Usually, the conversion is donethrough electrolysis.

One skilled in the art will readily appreciate that the presentinvention is well adapted to carry out the objects and obtain the endsand advantages mentioned, as well as those inherent therein. It will beapparent to those skilled in the art that various modifications andvariations can be made in practicing the present invention withoutdeparting from the spirit or scope of the invention. Changes therein andother uses will occur to those skilled in the art which are encompassedwithin the spirit of the invention as defined by the scope of theclaims.

1. A method for cleaning a process chamber for semiconductor and/or flatpanel display manufacturing, comprising: converting a feed gas to amixture of the feed gas and a cleaning gas in a device at a remotelocation and in fluid communication with the process chamber; separatingthe feed gas from the cleaning gas by liquefying the feed gas; anddelivering the cleaning gas to the process chamber.
 2. The method ofclaim 1, wherein the feed gas is HF.
 3. The method of claim 2, whereinthe cleaning gas is F₂.
 4. The method of claim 3, wherein saidconverting the feed gas is done by electrolysis.
 5. The method of claim1, further comprising exposing the cleaning gas to a remote plasmasource outside the chamber before said delivering the cleaning gas tothe process chamber.
 6. A method for cleaning a process chamber forsemiconductor and/or flat panel display manufacturing, comprising:converting a feed gas to a cleaning gas in a device in a remote locationand in fluid communication with the process chamber, wherein a resultinggas is a mixture of the feed gas and the cleaning gas; transferring theresulting gas to a trap, wherein the feed gas is converted into a liquidform, and the cleaning gas remains in a gaseous form; and delivering thecleaning gas to the process chamber.
 7. The method of claim 6, prior tosaid delivering the cleaning gas to the process chamber, furthercomprising: pumping the cleaning gas into a storage unit.
 8. The methodof claim 7, after said pumping the cleaning gas into a storage unit,further comprising: exposing the cleaning gas to a remote plasma sourceoutside the chamber before said delivering the cleaning gas to theprocess chamber.
 9. The method of claim 8, wherein said exposing isperformed through a source selected from the group consisting of aremote plasma source, a heat source, and an electrical source.
 10. Themethod of claim 9, wherein said remote plasma source is selected fromthe group consisting of a microwave energy source and a radiofrequencyenergy source.
 11. The method of claim 6, wherein the feed gas is HF.12. The method of claim 11, wherein the cleaning gas is F₂.
 13. Themethod of claim 12, wherein said converting the feed gas is done byelectrolysis.
 14. The method of claim 6, wherein the trap is a coldtrap.
 15. A method for cleaning a process chamber for semiconductorand/or flat panel display manufacturing, comprising: converting a feedgas comprising HF to a cleaning gas comprising F₂ in a device in aremote location and in fluid communication with the process chamber,wherein a resulting gas is a mixture of HF and F₂; tansferring theresulting gas to a trap, wherein the HF is converted into a liquid form,and the F₂ remains in a gaseous form; activating the F₂ outside thechamber to form atomic fluorine; and delivering the atomic fluorine tothe process chamber.
 16. The method of claim 15, prior to saidactivating the F₂, further comprising pumping the F₂ into a storageunit.
 17. The method of claim 16, wherein said activating is performedthrough a source selected from the group consisting of a remote plasmasource, a heat source, and an electrical source.
 18. The method of claim17, wherein said remote plasma source is selected from the groupconsisting of a microwave energy source and a radiofrequency energysource.
 19. The method of claim 15, wherein said converting the HF isdone by electrolysis.
 20. The method of claim 15, wherein the trap is acold trap.
 21. A method for cleaning a process chamber for semiconductorand/or flat panel display manufacturing, comprising: converting HF to F₂in a cleaning gas generator in a remote location in fluid communicationwith the process chamber, wherein a resulting gas is a mixture of the HFand the F₂; transferring the resulting gas to a trap, wherein the HF isconverted into a liquid form, and the F₂ remains in a gaseous form; anddelivering the F₂ to the process chamber.
 22. The method of claim 21,prior to said delivering the F₂ to the process chamber, furthercomprising: pumping the F₂ into a storage unit.
 23. The method of claim22, after said pumping the F₂ into a storage unit, further comprising:exposing the F₂ to a remote plasma source outside the chamber.
 24. Themethod ot claim 23, wherein said remote plasma source is selected fromthe group consisting of a microwave energy source and a radiofrequencyenergy source.
 25. The method of claim 21, wherein said converting theHF is done by electrolysis.
 26. The method of claim 21, wherein the trapis a cold trap.